Dissertation / PhD Thesis

FZJ-2026-04313

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Polyacrylonitrile-based Carbon Nanofibers for Gas Adsorption and Separation - Impacts of Thermal Stabilization and KOH Activation

Fischer, T. (Corresponding author)FZJ*RWTH*

2026
RWTH Aachen University

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Please use a persistent id in citations: doi:10.18154/RWTH-2026-00958

Abstract: The synthesis of polyacrylonitrile-based carbon nanofibers consists of the steps of electrospinning, thermal stabilization, carbonization and frequently an optional activation. This work focusses on the impacts of thermal stabilization and KOH activation on the pore structure and the CO2 adsorption properties of carbon nanofibers. Thermal stabilization parameters such as duration, temperature and atmosphere are investigated. A significant impact of these on the pore structure and thus the gas adsorption properties of the carbon nanofibers is found. Using several characterization techniques, such as infrared spectroscopy, elemental analysis and Raman spectroscopy, the incorporation of oxygen and the cyclization degree during stabilization are identified as key parameters, which affect the pore structure of the resulting carbon nanofibers. Besides thermal stabilization, KOH activation is thoroughly studied. Two O2-flow posttreatment conditions are applied to freshly KOH-activated samples directly after their activation to study potassium oxidation reactions. At high O2-flow, comparable to ambient air, vigorous oxidation causing an intense carbon combustion reaction is triggered. By application of a low O2-flow, the potassium oxidation was controlled and the carbon combustion reaction suppressed. Samples treated at low O2-flow conditions showed a distinct improvement of the gas adsorption properties. A series of KOH-activated carbon nanofibers at different degrees of activation is synthesized using low O2-flow post-treatment. The activation conditions result in a significant increase of narrow micropore volume and thus improved gas adsorption properties. The sample series is investigated in dynamic sorption experiments to study the separation of CO2 in binary CO2/N2 mixture at typical flue gas conditions. For higher KOH: Fiber activation degrees the CO2 selectivity decreased, resulting in a trade-off between adsorption capacity and selectivity. Besides the selectivity, the working capacity and cycle stability are evaluated in a simplified pressure swing adsorption cycle. All KOH-activated carbon nanofibers showed a sufficient stability and especially the most KOH-activated sample offers a highly improved working capacity compared to the pristine material at high adsorptive pressures. Overall, the work offers an important contribution to a more profound understanding of the possibilities for tailoring PAN-based carbon nanofibers for gas separation processes.

Keyword(s): Hochschulschrift ; adsorption ; gas separation ; carbon capture ; carbon nanofibers ; Kohlenstoffnanofasern

Note: Dissertation, RWTH Aachen, 2026

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Contributing Institute(s):

1. Grundlagen der Elektrochemie (IET-1)

Research Program(s):

1. 1232 - Power-based Fuels and Chemicals (POF4-123) (POF4-123)
2. HITEC - Helmholtz Interdisciplinary Doctoral Training in Energy and Climate Research (HITEC) (HITEC-20170406) (HITEC-20170406)

Appears in the scientific report 2026

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